Recently, there has been an increased interest in switchable glass, also known as smart glass. Switchable glass alters its light transmissive characteristics upon application of an appropriate voltage. For example, applying an electric potential difference (also referred to as a voltage) between two spaced apart parallel layers of a smart glass panel may cause the glass to switch from dark or opaque to transparent or translucent. Smart glass has been used, e.g., to provide “privacy windows” to adjust the privacy of homes and other buildings, or portions of them, such as changing or bathing rooms, showers, and the like. Similar concepts have been used to increase the energy efficiency of windows. For example, in the summer, smart glass may be used to reduce the amount of sunlight transmitted into a home or office building at midday, thereby reducing the workload on the air conditioning system required to keep the building cool.
Several smart glass technologies are being developed. For example, a suspended particle device (SPD) type of smart glass is typically dark or opaque in a non-activated state, and becomes transparent when activated in response to an applied voltage. States between high opaqueness (i.e., low transmittance) and high transparency (i.e., high transmittance) may be achieved by adjusting the applied voltage. While SPD-type smart glass has a fast response time when switching from a low-transmittance (i.e., high opaqueness) state to a high-transmittance (i.e., high transparency) state, SPD-type of smart glass has a slow response time when switching from a high-transmittance (i.e., high transparency) state to a low-transmittance (i.e., high opaqueness) state.
Another smart glass technology is liquid crystal technology. Similar to SPD-type smart glass, liquid crystal (LC) type smart glass is dark or opaque in the non-activated state, and becomes transparent when activated in response to a voltage being applied. While the response times associated with LC-type smart glass are relatively fast whether switching from a low-transmittance (i.e., high opaqueness) state to a high-transmittance (i.e., high transparency) state, or vice versa, LC-type smart glass has a much smaller range of transmittances (also known as a transmission range or a transmittance dynamic range) than SPD-type smart glass. For example, while the transmittance dynamic range of LC-type smart glass may be from roughly about 1 percent transmittance to 50 percent transmittance, the transmittance dynamic range of SPD-type smart glass may be roughly from about 1 percent transmittance to 80 percent transmittance, but is not limited thereto.